Calcium Carbonate and Gross-Size Analysis of Surface Sediments, Western Equatorial Pacific

Abstract

Surface-sediment samples taken from the tops of 47 free-fall, triggerweight, or piston cores from an area in the western equatorial Pacific (long 1550 E1750 E, lat 100 N-10° S) were separated into three size-fractions ( < 44 p" 44-246 p" > 246 p,), and the calcium carbonate content of the total sample and of each sizefraction was determined. Subaerial volcanic dilution from the direction of the Solomon Islands prompted exclusion of some samples from carbonate and sizefraction profiles. An abrupt decrease in carbonate content in the western equatorial Pacific occurs at 3,500 m, whereas the compensation depth is found at 5,250 m. Comparisons of previous works and examination of the present data prompt the assertion that, under specified conditions, the sedimentary lysocline may be approximated by the slope-break in plots of carbonate content versus depth. A strong positive correlation (0.92, P < 0.001) of the < 44-p, fraction with depth suggests that anomalous values for this weight-fraction may be useful in delineating displaced surface sediments in the area studied.